Does air resistance increase the speed of a falling object? I just saw an experiment where a heavy object (bowling ball) and a light object (feather) are dropped in a vacuum and they both fall at the same speed (almost like a slow motion video) and reach the bottom at the same time. But when the same two objects are dropped in a non vacuum environment, the ball hits the ground immediately while the feather has not even covered half the distance. I know this is somehow related to air resistance and terminal velocity and he air resistance reduces the acceleration of the ball to zero.  but what I do not understand is that how come air resistance helps in increasing the speed of the ball ? Isn't it a kind of resistance ? Is it that in the vacuum experiment, the ball reaches the ground very quick and only the video is in slow motion ?
Thought of adding the video link as well:
https://www.youtube.com/watch?v=E43-CfukEgs
 A: Well, the experiment was obviously filmed at a slower speed or shown at a slower speed. Both feather and ball should accelerate at around $9.8~\mathrm{m/s^2}$ and their velocities will be the same at all times. When there is air, the feather falls at much slower rate compared to the ball. Air resistance will decrease the acceleration of both but the effect of it will be much more on the feather.
A: Actually, to begin with, you were correct, @Crusaderpyro, in your question, that as the speed of a falling object increases, your air resistance increases. The reason this is is that as the object falls faster, it meets up with more and more air molecules per given amount of time. This will manifest as an increase in air resistance. However, we also have to include the factor of mass in the equation. Since the ball has more mass and less surface area, even though it also experiences more air resistance, it will be affected by gravity more and reach the ground before the feather, which has very little mass and more surface area and is therefore less affected by gravity. They both start accelerating at 9.8 m/s2, but the feather gets slowed down by the air resistance much more as you can see in the first part of the video, due its small mass and large surface area.
Of course, they slowed down the video in the second part, or the action would have been over in a fraction of a second. ( You can see this in the end of the video as they start to fall quickly together before the film gets slowed). But the main point was to show that, after the air is removed and thereby the air resistance removed, the ball and feather will fall at the same velocity.
